Dragonspine is a region of Mondstadt that released in 1.2 along with Albedo. The cryo hypostasis resides here (released v1.5).
The peak features the skyfrost nail, suspended midair, said to have dropped from Celestia, the floating island in the clouds.
There are three boxes hidden across Dragonspine (Princess, Priest, Scribe box). Collecting them will unlock a secret room in Starglow Cavern.
The princess box is obtained by touching a sword hilt and defeating some mages in northeast dragonspine. The scribe box is obtained by placing 3 cecilia flowers on a grave in the southwest. The priest box is obtained atop a broken castle in the west.
There is another secret room in Dragonspine, colloquially called the mural room. Here you can find the diagram for the snowtomber starsilver (a claymore for physical dps like Eula). Accessing the room requires activating tablets across dragonspine.
The first tablet can be found in the three box room. Interact with it to activate it.
The second tablet can be found at the top of the cavern by a ruin grader and torch lighting puzzle.
The third can be found in the cave below the cryo hypostasis. (To unlock the cryo hypostasis boss requires completing its own mini-puzzle.)
The fourth can be found by a torch (and ruin grader that appears once) south of Wyrmrest Valley.
The fifth can be found by the domain at Vindagnyr peak. Accessing the peak requires its own mini-quest.
The sixth tablet involves completing a puzzle with warming seelies. The goal is to light up all the ruin braziers using the seelies.
Around this area one can also obtain an ancient investigation journal, which will start another world quest.
The seventh tablet can be found northeast of the Frostbearing tree. The eighth and final tablet can be found inside the mural room.
Once all eight tablets are activated, one can open a locked door and obtain the snowtombed starsilver.
